Trichloroisocyanuric acid stabilized with hydrated sodium dichloroisocyanurate

ABSTRACT

A chlorine dry bleach having as its essential components trichloroisocyanuric acid and as a chemical stabilizer therefor hydrated sodium dichloroisocyanurate the water content of which is from about 7 to about 14%. The composition has excellent storage properties and generally good thermal stability and exhibits higher water solubility than trichloroisocyanuric acid alone. It can be used in any application calling for a source of active chlorine such as in water supplies for preventing the growth of pathogenic bacteria or as a bleach in detergents and as a sanitizing agent.

United States Patent [191 Berkowitz l l TRICHLOROISOCYANURIC ACIDSTABILIZED WITH HYDRATED SODIUM DICHLOROISOCYANURATE [75] Inventor:Sidney Berkowitz. Highland Park.

[73] Assignee: FMC Corporation, Philadelphia. Pa. [22] Filed: May 2,1973 [2 l] Appl. No; 356,350

Related [1.8. Application Data l63l Continuation-impart at Ser. No.309.599. Nm. 2-1.

I972. abandoned [52] US. Cl 252/187 C; 8/l08; 252/95 Int. CIR. CllD3/395; Cl [B 7/54: D06L 3/00 Field of Search 252/l87 C. 95. 98. I08;8/l08 {56] References Cited UNITED STATES PATENTS 198Gb}: -l/l9bl S) mes252/187 C 1 Nov. 11, 1975 3.(l35.(l57 StlJfiZ S \mes 252/l87 C 3.178.372-l/|96S Pomot 252/187 C 3.397.206 8/1968 Nicolaisen 252/]87 C Primarybiuuniueh-Benjamin R. Padgett .*l.\'.\'[.\'l(lllf Emutiller-Irwin Gluckl 57 1 ABSTRACT 3 Claims. N0 Drawings TRICI-ILOROISOCYANURIC ACIDSTABILIZED WITH IIYDRATED SODIUM DICI-ILOROISOCYANURATE CROSS REFERENCETO RELATED APPLICATIONS This is a continuation-in-part of Ser. No.309.599. filed Nov. 24. 1972. and now abandoned.

This invention relates to chlorinated isocyanurates, particularly toblends of hydrated sodium dichloroisocyanurate and trichloroisocyanuricacid.

The chlorinated cyanurie acids and their salts are well known as asource of active chlorine and are widely used in water supplies toprevent the growth of pathogenic bacteria in swimming pools and indetergent and sanitizing compositions. Of all the chlorinatedisocyanurates. trichloroisocyanuric acid has the highest chlorinecontent and accordingly is often the preferred member of the series.However. trichloroisocyanuric acid is susceptible to a peculiar type ofchemical instability as manifested by the evolution of noxious nitrogentrichloride fumes in the event the material remains in contact with air.It is generally conceded that moisture in the air is the causativefactor in the breakdown since the effect is less severe under desiccatedconditions.

It is known that the storage properties of trichloroisocyanuric acid canbe improved by the addition thereto of certain stabilizing substancesand in this connection reference is made to US. Pat. No. 3.278.443 onthe use of olefins; British Pat. No. l.197.689 on the use of sulfamates;and US. Pat. No. 3.342.684 on the use of metal carboxylates. Althoughgenerally satisfactory. such additives are objectionable in so far asthey act as diluents and thereby cut down on the available chlorine ofthe stabilized trichloroisocyanuric acid compositions. A chemicalcomplex of trichloroisocyanuric acid with potassium dichloroisocyanuratein the mole ratio of 1 to 4 of the type described in US. Pat. No.3,275,630 and which is a well known commercial dry bleach. whilesuperior in storage properties to the free acid. is objectionable inthat it undergoes self-sustaining. thermally initiated decomposition.The same applies generally to physical mixtures of trichloroisocyanuricacid and alkali metal dichloroisocyanurates.

It has now been discovered that the chemical decomposition oftrichloroisocyanuric acid can be greatly minimized without substantialsacrifice of available chlorine by blending the trichloroisocyanuricacid with an effective amount of hydrated sodium dichloroisocyanuratecontaining from about 7 to about 14% by weight of water of hydration.Considering the fact that moisture normally accelerates the chemicaldecomposition of trichloroisocyanuric acid, it is indeed most surprisingthat a hydrated salt with its relatively high water content would act asa chemical stabilizer. Moreover the water solubility of the mixture ishigher than that of the unstabilized trichloroisocyanurie acid and thisconstitutes another unexpected and beneficial property of suchcompositions. Where the hydrated sodium dichloroisocyanurate is thedihydrate. the compositions are not subject to self-sustaining thermallyinitiated decomposition.

In carrying out the invention the trichloroisocyanuric acid and hydratedsodium dichloroisocyanurate are blended together in the usual manner ofmixing solid 2 materials. Suitable mixing devices include rotatingtrays. ribbon blendors. tumblers or other low energy comminutingequipment. The mixture may also be compacted under pressure and thenground to the desired particle size for maximum homogeneity.

The proportion of the two components may vary con siderably. Forinstance. only a small amount of the hydrated sodiumdichloroisocyanurate is required to chemically stabilize thetrichloroisocyanuric acid. In general. satisfactory results can beachieved wherein the mixture contains any amount in excess of about liby weight of the hydrated salt.

As previously pointed out. in addition to their chemical stability. thecompositions of the invention possess greater water solubility thantrichloroisocyanuric acid alone. the solubility of the mixture rising asthe quantity of hydrated sodium dichloroisocyanurate is increased.Accordingly. the upper range of the hydrate will tend to be a compromisebetween solubility and chlorine content of the mixture. Thus. in theevent high chlorine content is desired that will require a greaterquantity of trichloroisocyanuric acid with concomitant lower solubility.If on the other hand. high solubility is required then more of thehydrate will be needed at the expense of available chlorine. Thoseskilled in the art will select the ratio of trichloroisocyanuric acid tohydrated sodium dichloroisocyanurate best suited to their particularneeds.

As understood herein. the term hydrated sodium dichloroisocyanurateencompasses sodium dichloroisocyanurate monohydrate. having a water ofcrystallization content of 7% and sodium dichloroisoeyanurate dihydratehaving a water of crystallization content of 14% as well as mixtures ofthe two hydrates.

In addition to their enhanced solubility and resistance to breakdownduring storage. the chemically stabilized trichloroisocyanuric acidcompositions of the invention are thermally stable. That is to say. thecompositions are not subject to the self-sustaining. thermally initiateddecomposition peculiar to anhydrous sodium dichloroisocyanurate. theactive agent in many dry bleach formulations which are soldcommercially. Such thermal stability is exhibited in any ratio oftrichloroisocyanuric acid to sodium dichloroisocyanuratc dihydrate.Compositions herein containing up to about by weight of sodiumdichloroisocyanurate monohydrate are likewise thermally stable as abovede scribed. The latter is rather unusual and unexpected since themonohydr ate itself undergoes self-sustaining. thermally initiateddecomposition. In other words. a mere l07r or so of trichloroisocyanuricacid suffices to arrest the thermal breakdown of sodiumdichloroisocyanurate monohydrate and to produce a chemically andthermally stable composition.

Reference is made to the following non-limiting examples.

EXAMPLE l A 500 ml Patterson-Kelly Twin Shell Blender was charged with300 gms of sodium dichloroisocyanurate dihydrate (20+70 mesh) and gms oftri chloroisocyanuric acid (20+7() mesh) and blended for l5 minutes. Theresultant product was a granular. free-flowing material which assayed64.0% available chlorine (theory 64.0%

Two hundred and fifty grams of the product was stored in a sealedcontainer at F for 8 days. Upon completion of the test. the product wasodorless. freeflowing with no evidence of any chemical decomposition.The product assayed 63.9% available chlorine.

EXAMPLE 2 Various concentrations of sodium dichloroisocyanuratedihydrateltrichloroisocyanuric acid blends were tested for progressive.thermally initiated decomposition. An l8 gage nichrome wire was embeddedin a 25 gram sample. The wire was heated by passing a current through itfor several seconds. until the material in contact with the wiredecomposed. The current was turned off and the decomposition wasobserved to determine the tendency for self-propagation.

The results ot'the tests at \arious concentration levels are listed inTable I.

TABLE l Sodium Dichloroisocyanurate Dihydrate l richloroisocyanuric AcidComposition eight I Decomposition lUU/(I incomplete 4U. to incompleteSo. It incomplete 7.535 incomplete hi3. incomplete 5th St! incomplete H.incomplete IUJNU incomplete ltlt ltt incomplete 5 incomplete U, llloincomplete Incomplete since the decomposition stopped alter the currentwas shut off with nlai r amounts of undccomposcd material remaining.Sample ol thi mi\ after prolonged thermal te t as al o incomplete Aswill be noted. none of the sodium dichloroisocyanuratedihydrate/trichloroisocyanuric acid formulations listed in Table lexhibit progressive. thermally initiated decomposition Such mixtures areboth thermally and chemically stable.

EXAMPLE 3 ln this example. the compositions of the invention werecompared to blends of various chlorinated isocyanurates with respect toprogressive. thermally initiated decomposition in accordance with theprocedure of Example 2. The results are listed in Table ll.

TABLE II EXAMPLE 4 Samples listed in Table II] were prepared containingby weight 8071 of the specified blends of chlorinated isocyanurates and20% by weight of selected grade red oak sawdust following the proposedBureau of Mlnes procedure RI 7594. In addition a control sample wasprepared with pure sawdust. Each sample was placed in a bed l 2X7 incheslong and ignited with a flame and rate of burning was timed. The resultsare listed in Table lll.

TABLE lll Chlorinated Proportions Burning lsocyanurate of Blend RateBlends Weight '1 lnJhlin.

l. Sawdust (control) 3.l

Chlorinated lsocyanurate Composition of lmcntion 2. Sodium dichloroiso-/25 ll cyanurate dihydrate, trichloroisocyanuric acid Chlorinatedlsocyanurate Compositions of Prior Art Sodium dichloroiso- 75/25 (1.7

cyanurate anhydrous. trichloroisocyanuric acid 4. Potassiumtlichloroiso- 75/25 (mt! cyanarate anhydrous trichloroisocy anuric acidAs is evident from the test results in Table III. the flammability offuel materials in contact with the thermally stable composition of theinvention (sample 2) is one-third that of corresponding anhydrousmixtures.

EXAMPLE 5 Various concentrations of sodium dichloroisocyanuratemonohydrate/trichloroisocyanuric acid blends were tested for progressivethermally initiated decomposition in the same manner as described inExample 2. Blends containing or less of the monohydrate did not exhibitthermal decomposition.

The results of these tests are listed in Table IV.

Compositions of lm ention 5. Sodium dichloroisocyanurtill/2U incompleteate dihydrate/trichloroisocyanuric acid 6. Sodium dichloroisocyanur-65/35 incomplete ate dihy drate 'trichloroisocy anuric acid complete andrapid decomposition complete and rapid decomposition complete and rapiddecomposition complete and rapid decomposition TABLE IV SodiumDichloroisocyanurate monohy drate/ trichloroisocyanuric Acid CompositionWeight i Decomposition lUU/(l Complete and rapid decomposition 95/5Complete and rapid decomposition 91)} H) Incomplete 75/25 IncompleteSit/5U Incomplete /75 lncomplete Iii/9U Incomplete 5/95 Incomplete U/HKJincomplete EXAMPLE 6 The purpose of this example is to demonstrate thechemical stability of chlorinated isocyanurates in terms of theirrelative propensity to release nitrogen trichloride when subjected to acontrolled moisture test. The test procedure was carried out as follows:

5 and 10 g quantities of the test specimen were each slurried in ml ofcarbon tetrachloride. Samples of the solution were withdrawn after about5 minutes and analyzed for the presence of nitrogen trichloricle bymeans of UV absorbtion against a UV standard for ni- 6 trogentrichloride. 20 and 40 ml of water were added respectively to the 5thoroughly H) g slurries and each thoroughly shaken. Samples of thecarbon tetrachloride solution were removed at about 5 minute intervals.then subjected to UV analysis to determine the amount of nitrogentrichloride therein. About four such samples were taken at five minuteintervals and so tested.

Based on the test procedure aforesaid a mixture of by weight sodiumdichloroisocyanurate and 25% by weight trichloroisocyanuric acidexhibited much higher chemical stability than trichloroisocyanuric acidalone.

Other compositions containing trichloroisocyanuric acid and sodiumdichloroisocyanurate exhibited comparable stability.

What is claimed is:

l. A chlorine dry bleach containing as its essential ingredientstrichloroisocyanurie acid and hydrates of so dium dichloroisocyanurateas a chemical stabilizer therefor at least about 1% by weight of thecomposition.

2. A composition according to claim l wherein the chemical stabilizer issodium dichloroisocyanurate monohydrate.

3. A composition according to claim 1 wherein the chemical stabilizer issodium dichloroisocyanurate dihydrate.

UNITED STATES PATENT OFFICE PATENT NO.

DATED INVENTOR(S) 1 November 11,

SIDNEY BERKOWITZ It is certified that error appears in theaboveidentified patent and that sard Letters Patent are hereby correctedas shown betow:

Column 1, line Column 2, line Columh 3, line 17 Column 6, line 2,

slurries and each [SEAL] 34, "3,342,684" should read 3,342,674.

21, "that" should read --this.

(Table I) "Dihydrate" should --Dihydrate/.

"5 thoroughly 10" should read -5 and 10g thoroughly shaken.-

Arrest:

RUTI'I C. MASON Arresting Offirer C. MARSHALL DANN Commissionerof'lan'nrs and Trademarks

1. A CHLORINE DRY BLEACH CONTAINING AS ITS ESSENTIALLY INGREDIENTSTRICHLOROISOCYANURIC ACID AND HYDRATES OF SODIUM DICHLOROISCYANURATE ASA CHEMICAL STABILIZER THEREOF AT LEAST ABOUT 1% BY WEIGHT OF THECOMPOSITION.
 2. A composition according to claim 1 wherein the chemicalstabilizer is sodium dichloroisocyanurate monohydrate.
 3. A compositionaccording to claim 1 wherein the chemical stabilizer is sodiumdichloroisocyanurate dihydrate.